The present invention relates to a shutter adapted to be attached to a television camera.
Most of currently used television camera tubes are storage-type camera tubes, which produce electric charges at their photoelectric surfaces when light arrives there, and which convert the electric charges to picture signals. After the loss of electric charges at the photoelectric surface by the scanning of one field, the storage-type camera tube electronically stores all incident light, projected on the photoelectric surface, as a picture for the next field until scanning of the next field is commenced. When a picture of a high speed object, such as a horce in race, is shot with a television camera using a camera tube of this kind, the camera tube converts a locus of the object to electric signals since the optical image of the object on the photoelectric surface moves during a time period between the scanning of a field and that of the next. This results in blurring of the object picture and hence details of the object cannot be clearly reproduced.
To overcome this drawback, there has been proposed a television camera shutter which is disposed on an optical axis and which is periodically released at a high speed in synchronism with a vertical drive signal of the television camera. An optical image for each field is projected on the photoelectric surface by every shuttering operation for a very short period of time. Thus, a clear picture is reproduced on a monitor screen by means of a video recorder, field memory, etc. FIG. 1 diagrammatically illustrates a typical example of this prior art shutter, in which two discs 100a and 100b which have each a pair of shutter holes 200a and 200b or 200b and 200b formed through them at intervals of 180.degree., are concentrically disposed and are rotated in the opposite directions. In this prior art shutter, corresponding shutter holes 200a and 200b of the two discs are designed to be aligned to each other on the optic axis O in synchronism with vertical drive signals of the television camera, thus allowing light to pass through them. However, this prior art shutter is disadvantageous in that the thickness thereof in the optic axis direction is rather large since two discs 100a and 100b are each provided with a drive unit for rotating them in the opposite directions. This results in that focusing of a short focal distance lens can be impossible. Further, the drive units are rather complicated in structure and hence increase weight of the television camera, which is disadvantageous in operation thereof.